ios - 为什么 Xcode 在控制台中打印 "[LogMessageLogging] "？

Question

为什么 Xcode 8 (iOS 10) 打印 [LogMessageLogging] <private>在控制台中，当我调用 map View 时？

[LogMessageLogging] <private>

谁能给点建议？

Answer 1

Privacy

The unified logging system considers dynamic strings and complex dynamic objects to be private, and does not collect them automatically. To ensure the privacy of users, it is recommended that log messages consist strictly of static strings and numbers. In situations where it is necessary to capture a dynamic string, you may explicitly declare the string public using the keyword public. For example, %{public}s.

• 来源:https://developer.apple.com/documentation/os/logging/generating_log_messages_from_your_code?language=objc
• WWDC 视频:https://developer.apple.com/videos/play/wwdc2016/721/?time=714

---

示例(ObjC):

os_log_t log = os_log_create("com.example.my-subsystem", "test");

const char *staticString = "I am static string!";
const char *dynamicString = [[NSString stringWithFormat:@"I am %@!", @"dynamic string"]
                             cStringUsingEncoding:NSUTF8StringEncoding];

os_log(log, "Message: %s", staticString);
os_log(log, "Message: %s", dynamicString);
os_log(log, "Message: %{public}s", dynamicString);

// Output
// [test] Message: I am static string!
// [test] Message: <private>
// [test] Message: I am dynamic string!

---

示例( swift ):

目前，Swift 中的日志记录字符串似乎已损坏(https://openradar.appspot.com/radar?id=6068967584038912)，因此我们需要手动将 C 函数桥接到 Swift:

更新 01。 Radar 28599032 已修复，不适用于 Xcode 10。

// File: os_log_rdar28599032.h
#import <Foundation/Foundation.h>
#import <os/log.h>

void log_private(os_log_t, os_log_type_t, NSString *);
void log_public(os_log_t, os_log_type_t, NSString *);


// File: os_log_rdar28599032.m
#import "os_log_rdar28599032.h"

void log_private(os_log_t log, os_log_type_t type, NSString * message) {
   os_log_with_type(log, type, "%s", [message cStringUsingEncoding:NSUTF8StringEncoding]);
}

void log_public(os_log_t log, os_log_type_t type, NSString * message) {
   os_log_with_type(log, type, "%{public}s", [message cStringUsingEncoding:NSUTF8StringEncoding]);
}


// File: ViewController.swift
import Cocoa
import os.log
import os.activity

class ViewController: NSViewController {

   static let log = OSLog(subsystem: "com.example.my-subsystem", category: "test")
   typealias SelfClass = ViewController

   override func viewDidLoad() {
      super.viewDidLoad()
      log_private(SelfClass.log, .fault, "I am dynamic \("string")!")
      log_public(SelfClass.log, .fault, "I am dynamic \("string")!")
      log_private(SelfClass.log, .fault, #file)
      log_public(SelfClass.log, .fault, #file)
   }

}

// Output
// [test] <private>
// [test] I am dynamic string!
// [test] <private>
// [test] /[REDACTED]/ViewController.swift